IP is best effort. Packets get lost all the time. Higher protocols, like TCP and QUIC, all handle packet loss--typically by trying again. Losing a packet is better than losing all open connections.

I think it may be worse than a lost packet, though. If the destination host is truly gone from that network, the nearest router might reply that no such computer exists, causing the socket to be disconnected. (It's been awhile since I've studied TCP/IP; I'm not sure what the exact correct reply would be...)

Perhaps this could be mitigated by adding a timeout that keeps sockets alive for awhile in case the destination shows up somewhere else.

In a sensible (i.e., NAT-free) world, the end point knows when its global address changes, which it can use to trigger an address update to its peer.